Typically, a squirrel cage amortisseur winding is built into rotors for synchronous dynamoelectric machines in order to start it and bring it up close to synchronous speed. In one design, the rotor is designed from laminations which are axially aligned and stacked, the laminations having pole pieces around which wire is wrapped to form the field windings on the rotor. In the pole pieces, a series of axially aligned holes are provided for the insertion of conductor bars which form the cage portion of the squirrel cage amortisseur winding. At each end of the lamination stack, end plates are mounted to the rotor which are electrically conductive and which are welded or otherwise secured to the conductor bars to electrically connect them to complete the electrical circuit of the winding. In the prior art, these end plates are typically cast aluminum or the like. Some prior art designs are of plate-type construction similar to a lamination. However, they are all one piece designs.
One such design in the prior art which has been used by the assignee of the present invention is a one-piece end plate which is approximately 13" in diameter and which is formed by plasma torch cutting a 4'.times.8' sheet of aluminum alloy 1100. The 4'.times.8' pre-formed sheets are the industry standard and they are made from 99% pure aluminum. Recently, the price of these sheets has escalated quite dramatically such that there is a significant amount of money in wasted material caused by laying out the one-piece, circular end plates in routine fashion across the 4' width of a standard sheet. As is apparent, three full end plates may be laid across the width of the plate, but that leaves 9" of waste material at one side of the plate. Additionally, there is waste throughout the length of the plate as seven 13" diameter end plates can be laid out in an 8' dimension which leaves 5" of waste. While some small portion of this waste can be saved by strategically positioning the circular end plates across the face of the plate, there is still quite a significant amount of waste due to the fact that the diameter of the end plate does not accommodate close spacing of the end plates to the edge of the sheet in either the width or length dimension.
To solve these and other problems in the prior art, the inventor herein has succeeded in designing and developing a multi-piece end plate for an amortisseur winding which generally consists of four angular segments, each segment being shaped exactly the same such that it forms 90.degree. of the 360.degree. arc of the end plate. Furthermore, and perhaps more significantly, the inventor has designed the segment such that a non-functional portion of the segment lies at each edge of its width, thereby permitting the edges to be lopped off or cropped to fit within a smaller envelope of space which can be lined up across the width of the plate to exactly 48", the industry standard for the raw material. This dramatically reduces the amount of waste over that created by cutting out in the prior art one-piece circular design. Furthermore, as only a non-functional portion of each segment is eliminated, this does not interfere with the electrical operation of the end plate. Functionally, the purpose of the end plate is to electrically connect the conductor bars forming the squirrel cage amortisseur winding. These conductor bars are positioned generally apart from a radially extending center line through each pole piece of the end plate. Thus, a substantially triangular portion of the outer edge at this center line of each pole plate can be eliminated as no conductor bars are joined to the end plate in that location.
To further reduce waste, part of the annular collar which surrounds the motor shaft is cut away such that as the segments are lined up along the length dimension of the sheet, the pole pieces of the adjoining segment overlap these annular portion cutaways. With this technique, the segments may be placed even closer together along the length of the plate which helps minimize waste in the length dimension of a standard 4'.times.8' sheet.
In order to facilitate assembly of four segments into a single end plate, a tab is formed along the radial center line of each pole piece which interfits into a slot in an adjacent segment, the adjacent segments may then be staked or welded to join them and thereby form a single piece end plate assembly.
While the principal advantages and features of the invention have been explained above, a more fuller understanding of the invention may be attained by referring to the drawings and description of the preferred embodiment which follow.